Inclusion complexation of 2-(4′-N,N-dimethylaminophenyl)-1H-naphth[2,3-d]imidazole by β-cyclodextrin:: effect on the twisted intramolecular charge transfer emission

Spectral characteristics of 2-(4'-N,N-dimethylaminophenyl)-1H-naphth[2,3-d] imidazole (DMAPNI) have been studied in aqueous beta-cyclodextrin (beta-CDx) solution. Enhancement in the fluorescence intensity of the normal band (B) is more than that of the twisted intramolecular charge transfer (TICT) band (A). pK(a) value for the protonation of =N-atom and the blue shifts observed in both the fluorescence bands suggest the encapsulation of DMAPNI in the hydrophobic cavity of beta-CDx. Steady state and time resolved spectral analysis support the formation 1:2 complex between DMAPNI and beta-CDx. Enhancement in the fluorescence intensity in aqueous beta-CDx solution is due to the decrease in the non-radiative processes. (C) 2002 Elsevier Science B.V. All rights reserved.